The present embodiments relate to a particle therapy system.
A particle therapy system (installation) may be used to irradiate a patient with a particle beam. H. Blattmann in “Beam delivery systems for charged particles,” Radiat. Environ. Biophys. (1992) 31:219-231 discloses various irradiation systems and techniques. EP 0 986 070 discloses a particle therapy system.
Japanese Patent Disclosure JP 11009708 A discloses an irradiation therapy system, in which a patient positioning device is located between a magnetic resonance scanner and the gantry of a treatment system.
A particle therapy system includes an accelerator unit and a high-energy beam guiding system. A synchrotron or a cyclotron is used to accelerate the particles, such as protons, pions, or helium, carbon or oxygen ions.
The high-energy beam guiding (transport) system carries the particles from the accelerator unit to one or more treatment chambers. In a “fixed beam” treatment chamber, the particles reach the treatment site from a fixed direction. In a gantry-based treatment chambers, the particle beam may be aimed at the patient from various directions.
The particle therapy system includes a monitoring and safety system that assures that a particle beam, which is characterized by the required parameters, is carried into the appropriate treatment chamber. The parameters are defined in a treatment or therapy plan. The plan indicates how many particles, from what direction, and how much energy, should strike the patient.
The therapy plan is created using an image data set. For instance, a three-dimensional (3D) data set is created with a computed tomography scanner. The tumor is located within the image data set, and the required radiation doses and directions of incidence are decided based on the image data set.
During the radiation treatment (irradiation), the patient assumes an irradiation position on which the treatment planning was based. For a fixation mask is used. Before the irradiation, the position of the patient is checked with an imaging device. The current irradiation position may be calibrated with the image data set on which the treatment planning was based.
Before the radiation treatment (irradiation), images from various directions are calibrated, for example, with projections from a CT planning data set. Scans may be made in the beam direction and orthogonally to the beam direction. The scans are made in the irradiation position near the beam exit. There may be only a limited amount of space for the imaging.
A 3D image data set may be obtained based on performing scans from various directions. From the image data, a 3D image data set may be obtained, similarly to a CT scan. For scanning a patient from various directions, an imaging robot arm may be aimed freely around a patient. Another option is obtaining a 3D image data set using a C-arm X-ray machine, for example.
The imaging units for obtaining 3D image data sets from various directions require enough space to enable scanning the patient from different directions. Elements of the imaging unit are capable of being moved around the patient at a sufficient distance for imaging.
In particle therapy, patient is positioned close to the beam exit, to keep the flaring of the stream from scattering. For example, a typical spacing between the isocenter of an irradiation site and the beam exit is approximately 60 cm.
The spacing between the isocenter of an irradiation site and the beam exit restricts the imaging for position verification to imaging devices that occupy correspondingly little space.